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Kellett, Cameron William

University of British Columbia

Electron transfer reactions in solution and electron transport in solid-state devices often involve electron transfer events between distinct molecules or otherwise through interfaces between disparate materials. The performance of electronic materials and redox catalysts relies in part on fast intermolecular electron transfer. The electronic coupling (HDA), between electron donors and acceptors is a crucial factor in determining the rate of electron transfer reactions, yet, among the many factors influencing intermolecular electron transfer kinetics, this property is arguably the most challenging to reliably engineer. While it is well understood that HDA can be influenced by the nature of weak intermolecular interactions between the reactants in intermolecular electron transfer reactions, universal structure-property relationships that can be applied to modulate HDA through any interaction in any situation have yet to be developed. For ground-state intermolecular electron transfer reactions, HDA of a reacting donor-acceptor pair in their reactive geometry can be approximated from the overlap integral between their frontier molecular orbitals. In this thesis, I show that this approximation can serve as a useful intuitive tool for researchers designing high-performance electronic materials. In order for a particular intermolecular interaction to increase HDA, it is necessary that the frontier molecular orbitals of the electron donor and acceptor are significantly delocalized onto the atoms involved in that reaction. Moreover, the extent to which those atoms are involved in the frontier molecular orbitals can serve as a rough quantitative predictor of the relative magnitude of HDA through those interactions. I demonstrate, through the use of this principle, how careful design of molecular electron acceptors can accelerate the rate of iodide oxidation through non-specific chalcogen-iodide interactions or through halogen bonding interactions. A surprising consequence of this research was the discovery that halogen bonds can involve not just a σ-symmetric covalent component, but a π-symmetric component as well. Experimental evidence of this π-covalency in a halogen bond and the potential implications of this discovery are discussed in the final chapters.

Text

2023-10-03

Attribution-NonCommercial-NoDerivatives 4.0 International

http://hdl.handle.net/2429/86055

Chemistry

University of British Columbia

UBCV

http://creativecommons.org/licenses/by-nc-nd/4.0/